ABSTRACT One of the most robust findings in the speech literature is that aging decreases audiovisual speech recognition, even when auditory-only performance is controlled. To understand why this happens, most researchers have focused on audiovisual integration, assuming that there is a distinct integration stage and that integrative ability diminishes with age. Our most recent findings, however, reveal that unimodal performance, not diminished integrative abilities, accounts for the age-related decline in audiovisual speech perception. Accordingly, the research proposed for this grant cycle is based on a new theoretical model, developed during the last grant cycle, which emphasizes the role of age-related differences in vision-only perception in audiovisual speech recognition. In our experimental methods, we will take the unique tact of using lipreading skill as a fundamental independent variable. For Specific Aim 1, we will use our new feature analysis methods to predict audiovisual speech recognition based on participants' auditory-only and vision-only performance. Further, we will evaluate the relative contributions of cognitive, perceptual, and speech production abilities to both age-related and individual differences in vision-only and audiovisual performance. For Specific Aim 2, we will use our novel priming task and our lipread-yourself task, along with fMRI, to demonstrate that aging diminishes the correspondence between the phonological representations that support speech production and perception. Finally, for Aim 3, we will identify neural correlates of vision-only and audiovisual speech perception using fMRI. The results from Aims 1 and 2 will help us to identify regions of interest that may account for age-related and individual differences in performance. We predict that older adults who are good lipreaders will show similar activation patterns to young adults who are good lipreaders, but that older adults in general will show different patterns of activation. By the end of the grant cycle, we will become the first researchers to develop a unified neurocognitive framework for understanding the age-related differences in vision-only and audiovisual speech perception We will support the model with both behavioral and fMRI data. Understanding age-related changes in audiovisual speech processing is critical because of its clinical utility, providing guidance for both speech perception training curricula and aural rehabilitation counselling, and because sensory and cognitive changes in aging can shed new light on our theoretical understanding of speech perception. Our multidisciplinary team of cognitive scientists and aural rehabilitation specialists are uniquely poised to develop and fine-tune a unified neurocognitive model of aging and audiovisual speech perception.